Deadzone-adapted disturbance suppression control for global practical IOS and zero asymptotic gain to matched uncertainties

Abstract

For control-affine nonlinear systems with a disturbance and unknown parameters satisfying a matching condition but not having a known bound, we introduce a direct adaptive control scheme with three design elements: (a) nonlinear damping, (b) single-gain adjustment, and (c) deadzone in the update law. Combining these three ingredients for the first time, we guarantee the following previously unattained property: an attenuation of the plant state to an assignable small level, despite unknown bounds on the parameters and disturbance, without a drift of the gain, state, and input. Given the tools and results, we refer to the proposed scheme as a Deadzone-Adapted Disturbance Suppression (DADS) Controller.